Single use syringe

ABSTRACT

A single use retractable syringe and plunger are provided. The syringe has a barrel having a collar with one or two projections that slidably engage a plurality of interconnected slots of the plunger. The slots of the syringe include one or more gates or abutments that restrict slidable movement of the projections within the slots to thereby prevent re-use of the syringe after injection and subsequent retraction of the needle.

This application is a national stage application under 35 U.S.C. § 371from PCT Application No. PCT/AU01/00458, filed Apr. 20, 2001, whichclaims benefit under 35 U.S.C. § 119 from Australian Application PR2591,filed Jan. 18, 2001, and Australian Application PQ7096, filed Apr. 26,2000.

FIELD OF THE INVENTION

THIS INVENTION relates to syringes. In particular, this inventionrelates to a single use syringe and, more particularly, to a single useretractable syringe and plunger therefor.

BACKGROUND

The problems of shared syringes are notorious. The practice of sharingsyringes without adequate sterilization between successive users is amajor contributor to the transfer of Human Immunodeficiency Virus andHepatitis with subsequent severe repercussions for the sufferer of suchdiseases and at a high cost to society of supporting and providingmedical attention to those sufferers.

A lesser but still significant risk associated with unclean needles andsyringes arises from the possibility of inadvertent needle-stickinjuries. This is particularly a problem for law enforcement officersand paramedics who often encounter users of illegal drugs in theirprofessional activities. Additionally, the habits of illegal drug usersare such that dangerous byproducts of their activities, such asdiscarded syringes, are often left in places of public access presentinga risk to the users of areas such as public parks and school grounds.

There is clearly a need for an effective single use syringe which notonly minimizes the chance of people sharing syringes, but also retractsa delivery needle into the syringe barrel, thereby inactivating thesyringe and shielding the needle from inadvertent, harmful contact withother people.

Australian Patent Application No 86142198 (incorporated herein byreference in its entirety) to the present applicants discloses a singleuse syringe which goes a considerable way to addressing the aboveproblem by providing a syringe barrel and plunger co-operating to rotatethe plunger during use. When the plunger is rotated from its originalorientation, a needle grasping mechanism is aligned with a receivingmeans in the needle seat. Once engaged by the grasping mechanism, theneedle is retracted into the syringe barrel by retraction of theplunger.

However, the present inventors are aware that it is possible for anassiduous delinquent to re-use the above syringe by avoiding fulldepression of the plunger or by ensuring rotation of the plunger backinto its original orientation during depression so that engagement ofthe plunger and needle does not occur.

SUMMARY OF THE INVENTION

In one aspect, the invention provides a plunger for a single use syringehaving a co-operating barrel that has at least one projection, saidplunger comprising a plurality of interconnected slots slidablyengageable by said at least one projection, arranged so that slidablemovement of said at least one projection within said slots is restrictedto thereby prevent re-use of the syringe.

In another aspect, the invention provides a collar for a single useretractable syringe having a co-operating plunger that has at least twoslots, said collar comprising first and second guiding projectionsslidably engageable with said at least two slots of said co-operatingplunger.

In yet another aspect, the invention provides a single use retractablesyringe having a plunger according to the aforementioned aspect.

Preferably, the plunger is for a single use syringe having a retractableneedle that can be engaged by said plunger to facilitate retraction ofthe needle.

Preferably, the plunger comprises a movement restriction means thatrestricts slidable movement of said at least one projection within atleast one of said plurality of slots.

Preferably, said movement restriction means may comprise one or moregates or abutments.

In one embodiment, the plunger is for a single use syringe having aco-operating barrel that has a single projection.

In this embodiment, said plurality of interconnected slots comprises afirst slot and a second slot, said first slot deviating to meet saidsecond slot.

Preferably, the plunger further comprises a gate that restricts movementof the projection from the second slot into the first slot.

Preferably, the plunger further comprises one or more gates or abutmentsin the second slot that upon engagement by said projection restrictwithdrawal of the plunger.

Preferably, the plunger further comprises a retraction slot, connectedby a deviation to the second slot, that facilitates retraction of theplunger.

In another embodiment, the plunger is for a single use syringe having aco-operating barrel that has first and second projections.

In this embodiment, said plurality of interconnected slots comprises afirst slot, a second slot, a retraction slot and a fourth slot.

According to this embodiment, it is preferred that the retraction slotis connected by a deviation to said second slot, thereby facilitatingcomplete retraction of said plunger.

Preferably, the first slot and the retraction slot each include anabutment engageable by said second projection and said first projectionrespectively, to prevent re-use of the syringe.

Preferably, the second slot includes a plurality of abutments engageableby said first projection to restrict withdrawal of the plunger.

Throughout this specification, unless otherwise indicated, “comprise”,“comprises” and “comprising” are used inclusively rather thanexclusively, so that a stated integer or group of integers may includeone or more other non-stated integers or groups of integers.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to theembodiments disclosed in the accompanying drawings, wherein:

FIG. 1 is a schematic cross-sectional elevation view of retractablesyringe disclosed in AU 86142/98;

FIG. 2 is a side view of the plunger of the retractable syringe of afirst embodiment of the present invention;

FIG. 3 is an enlarged view of the syringe plunger of FIG. 2;

FIG. 4 is a detailed view of the junction between a first and secondslot in the syringe plunger of FIG. 2;

FIG. 5 is a detailed view of the junction of a first and second slot ina further embodiment of a syringe plunger of the invention;

FIG. 6 is a top view of a still further embodiment of a plunger of theinvention;

FIG. 7A is a side view of a portion of the plunger of FIG. 6 and acorresponding guiding projection of a syringe barrel wherein a secondslot of the plunger comprises a single abutment in the form of a ramp;

FIG. 7B is a side view of another portion of the plunger of FIG. 6 and acorresponding guiding projection of a syringe barrel wherein a secondslot of the plunger comprises a plurality of ramps;

FIG. 8 is a top view of a collar for use with a syringe barrel;

FIG. 9 is a sectional view of the collar of FIG. 8 taken along the line9-9;

FIG. 10 is a sectional view of a part of the collar of FIG. 8 takenalong the line 10-10;

FIG. 11A is an exploded perspective view of one side of a plunger andcollar;

FIG. 11B is an exploded perspective view of another side of the plungerand the collar shown in FIG. 11A;

FIG. 11C is another exploded perspective view of the plunger and collarshown in FIG. 11A;

FIG. 11D is yet another exploded perspective view of the plunger and thecollar shown in FIG. 11A;

FIG. 12 is an exploded perspective view of a retractable single usesyringe;

FIG. 13 is a sectional view of a collar having first and second guidingprojections;

FIG. 14A is a sectional elevation view of a plunger and collar havingfirst and second projections during initial depression of the plunger toexpel air from the barrel;

FIG. 14B is a sectional elevation view of the plunger and collar afterinitial withdrawal of the plunger to fill the syringe barrel;

FIG. 14C is a sectional elevation view of the plunger and collar afterneedle retraction; and

FIG. 15 is a perspective view of a plunger and collar showing aplurality of abutments in a second slot of the plunger.

DETAILED DESCRIPTION

In FIG. 1 there is shown a prior art retractable syringe 10, asdisclosed in Australian Patent Application No 86142/98, which isincorporated herein by reference, syringe 10 comprising a hollow barrel12, a needle 13 engaged with needle end 14 of plunger 15 that isslidably disposed in the hollow barrel 12. The plunger 15 is engageablewith needle 13 so as to enable disengaging of needle 13 from barrel 12as the plunger 15 is retracted following use. Retraction of the plunger15 with which the needle 13 is engaged, draws the needle 13 into thehollow barrel 12, thus preventing accidental puncture of the skin withthe used needle 13 or re-use by intravenous drug users.

In use, the plunger 15 is initially depressed towards the hollow barrel12 needle end 14 to expel any air from the barrel 12. At the end of thisinitial depression, the plunger 15 does not engage the needle 13 so thatthe needle 13 remains engaged with barrel 12. Fluid to be injected isthen drawn into the hollow barrel 12 through the needle 13 in the usualmanner as the plunger is initially retracted.

To provide for the radial non-alignment of corresponding interlockingportions 20,21 on the initial depression of the plunger 15 to expel air,and for radial alignment on the subsequent depression of the plunger 15to dispense fluid, a projection (not shown) sequentially engages firstslot 16 and second slot 17 provided on the plunger 15. The projection isprovided on collar 18 mounted onto the guiding end 19 of the barrel 12during assembly of the syringe 10. The projection extends radiallyinwardly from collar 18 through which the plunger 15 slides. The collar18 is fitted to barrel 12 such that the projection initially engages thefirst slot 16 prior to use, with engagement of the projection and firstslot 16 radially non-aligning the corresponding interlocking portions20, 21 such that they will not engage on initial depression of theplunger 15 to expel air from the hollow barrel 12.

The first slot 16 longitudinally extends from the guiding end 19 ofplunger 15 to partway along the plungers length where the first slot 16deviates circumferentially to meet the second slot 17. As a result ofthe deviation of the first slot 16 as plunger 15 is retracted to receivefluid into the hollow barrel 12 directly following its initialdepression, the projection (not shown) on collar 18 will be guided fromthe first slot 16 through the deviation 23 and into the second slot 17.As the projection is fixed, this will result in the plunger beingrotated through 90° so that the corresponding interlocking portions 21,20 of the plunger 15 and needle 13, respectively align. The second slot17 longitudinally extends along plunger 15 toward needle end 19. On thesubsequent depression of the plunger 15 to dispense fluid, thecorresponding interlocking portions 20, 21 will engage at the end of thestroke enabling disengagement of the needle 13 from barrel 12 andretraction of the needle 13 into barrel 12 as the plunger 15 isretracted.

An embodiment of a plunger 115 for a single use retractable syringe 110according to the present invention is shown in FIG. 2 and FIG. 3. Collar118 and projection 122 are best seen in FIGS. 7-10.

Referring to FIG. 2, first slot 116 second slot 117 are interconnectedby first deviation 123. As noted previously in the prior art retractablesyringe, it is possible for a drug abuser to redirect the plunger 115during depression so that slot 116 is again engaged with the projection122 so that full depression of the plunger 115 can occur withoutretraction of the needle.

To prevent this possibility, the inventors have inserted gate 124 atfirst deviation 123. The function of gate 124 is to allow passage of theprojection 122 into slot 117 but to then prevent its re-entry into slot116 after rotation of the plunger 115. After entry of the projection 122into slot 117, plunger 115 will be permanently positioned so thatcorresponding interlocking portions on the plunger and needle (not shownin FIG. 2) are aligned.

The present inventors also note that it is possible for a syringe asdisclosed in Australian Patent Application No 86142/98 to be used morethan once if a user avoided full depression of plunger 115 in barrel112. This restraint avoids engagement of the corresponding interlockingportions.

To create a means of preventing such use, the present inventors haveprovided gates 125A, 125B, 125C, 125D in second slot 117. These gatesare offset in a direction that allows projection 122 on collar 118 topass along slot 117 and through the gates 125A-D towards the end of theplunger 115 distal to needle end 114. That is, the gates 125A-D allowdepression of the plunger 115. However, whenever the projection 122passes through gate 125, it is blocked from re-entry into the portion ofthe slot 117 that it just exited by abutting one of gates 125A, B, C orD. That is, withdrawal of the plunger in the barrel is prevented bygates 125A-D.

However, as the plunger 115 is depressed and the interlocking portions(not shown) are aligned, the plunger 115 engages the needle forretraction. The plunger 115, however, cannot be withdrawn along slot 117because of the presence of the gates 125A-D against which projection 122abuts. A retraction slot 129 is therefore provided to allow retractionof the plunger 115 when engaged with the needle of the syringe.Retraction slot 129 and second slot 117 are interconnected by seconddeviation 128.

Referring now to FIG. 3, sliding movement of projection 122 from firstslot 116 to second 117 is straightforward. However, any attempt toslidably move the projection 122 back into first slot 116 will encountergate 124. Any attempt to force gate 124 will lead to its jamming againstthe wall 126 of deviation 123. Any subsequent additional force appliedis unlikely to be successful in forcing the projection 122 back intoslot 116. Even if the integrity of gate 124 is destroyed, it is likelythe deformed gate will jam, thereby preventing further use of thesyringe 110. Gates 125A-D operate on a similar principle. However, gates125A, B and C are situated adjacent respective recesses 127 A, B and Cin the substantive structure of the plunger 115. These recesses providea nesting position for projection 122. Recesses 127 A-C also provideclearance for adjacent gates 125 during passage of projection 122 sothat the gates 125 clear slot 117. For example, gate 125B does notobstruct the passage of projection 122 when forced into recess 127C.

As shown in FIG. 2 and FIG. 3, gate 125D adjoins second deviation 128into retraction slot 129. Retraction slot 129 allows retraction of theplunger 115 (and an engaged needle) once fully depressed afterprojection 122 has proceeded through gate 125D and second deviation 128.Second deviation 128 between second slot 117 and retraction slot 129 iscircumferential and movement of projection 122 therethrough drivesfurther 90° rotation of the plunger 115. At this point, the needle ispositively engaged with the plunger 115. The needle 113 may then besafely retracted into the barrel 112 of the syringe 110 by retraction ofplunger 115 until the projection 122 encounters terminal wall 130 ofretraction slot 129.

In FIGS. 4 and 5, there are shown various configurations of gate 124 andgates 125A-D. In FIG. 4, scalloped undercut 131A is present in gate125A, and scalloped undercut 131B is present in gate 124. Theseundercuts provide respective soft hinges to facilitate easy operation ofthe plunger 115. This view also shows the outer edges 132A and 132B ofoffset gate 125A and gate 124 respectively, which are substantiallyparallel to adjoining surfaces 133A and 133B respectively. Thisincreases the area of contact should any attempt be made to force theguiding projection in an undesired direction.

Referring to FIG. 5, gate 125A has a front face 134 and rear face 135.Rear face 135 describes an arc which gives an increased thickness to thegate 125A and thereby increases its strength. This also provides asmooth curved entry into recess 127A for projection 122 shouldretraction be attempted after the projection 122 has passed gate 125A.It is again clear in this view that gate 125A will hingedly move intorecess 127A during passage of projection 122.

In FIGS. 6, 7A, and 7B there are shown other means by which retractionof plunger 115 may be restricted or prevented when projection 122engages second slot 117.

FIG. 6 is a part view of an embodiment of plunger 215 of the inventionin which offset gates 225A-D in slot 217 are replaced by a series ofabutments such as ramps 250A-C. Each ramp 250 terminates in curved face251 rising from the base 252 of second slot 217. Also present are ledges253A and 253B located at the junction of deviation 223 and second slot217 and at the junction of second slot 217 and second deviation 228respectively.

It is noted that during initial retraction, projection 222 slidablymoves from first slot 216 into first deviation 223 and then across ledge253A into second slot 217. Projection 222 is thereby restrained fromre-entry into first deviation 223 by abutting against ledge 253A.Furthermore, projection 222 slidably moves from second slot 217 acrossledge 253B into second deviation 228. Projection 222 is therebyrestrained from re-entry into second slot 217 by abutting against ledge253B.

FIG. 7A is a side sectional view of a ramp 250 of the embodiment of FIG.6, wherein projection 222 is in the form of an arm having a proximalmember 254, an elbow 255 and a distal member 256. Distal member 256terminates in a curved surface 257 which is complementary to curved face251 of ramp 250. In operation, guiding projection 222 is resilient andslides along base 252. As the plunger 215 is retracted in the directionindicated by the arrow, projection 222 is displaced by the ramp 250. Theprojection 222 is tensioned as it is slid up the ramp 250. Projection222 then flicks or snaps into engagement with base 252 of slot 217 onceit has cleared the ramp 250. Engagement between complementary curvedface 251 of ramp 250 and curved surface 257 of projection 222 prevents,or at least makes more difficult, any attempt to depress the plunger 215subsequent to its withdrawal after use.

It will be appreciated by the skilled person that the number of ramps250 or offset gates 125 present may be varied as desired and that thenumber described herein is merely for the purposes of illustration. FIG.7B shows multiple ramped abutments 350A, B and C each having arespective plateau 358, in contrast to the continuously-sloped ramp 250shown in FIG. 7A.

FIG. 8 shows a top view of collar 118 suitable for use with a syringebarrel in the present invention. Although the collar 118 is described asseparate from the barrel, it is understood that reference to a barrel inthis specification will, where appropriate, include reference to abarrel and collar. While it is possible to mount the projection on thebarrel itself, it is more efficient and practical to do so on collar 118for use with the syringe.

Collar 118 has a central aperture 160 for location of a plunger 115according to the present invention. The collar 118 also has a body 161and an upper circular wall 162 which defines a seat 165 for receivingplunger 115. The collar 118 has an outer wall 163 which is continuouswith barrel-engaging arms 164A, 164B seen in hidden detail. Projection122 extends into the aperture 160.

FIG. 9 is a sectional view taken along the line 9-9 and shows theprojection 122 with curved end 157. Wall 162 defines seat 165 forreceiving an end of a syringe plunger. The body 161 is continuous withthe barrel-grasping arms 164A and 164B which respectively terminate inhooks 166A and 166B.

FIG. 10 is a sectional view of a part of the cap of FIG. 8 taken alongthe line 10-10. This view shows projection 122 formed by proximalportion 154, elbow 155 and distal portion 156 terminating in curved end157. The elbow forms an angle of slightly greater than 90° that theprojection slopes towards the surface of a co-operating plunger (notseen). Preferably, projection 122 is resiliently flexible so thatdisplacement of the end 157 when engaging a ramp 150, for example, willbe followed by a flick back once the projection 122 clears the ramp 150.The distal portion 156 will be displaced radially outwardly by such aramp followed by a radially inwards snap rebound on passage of ramp 150.

The radius on the end of projection 122 helps turn the plunger 115relative to the barrel 112 when it travels from the first slot 116 tothe second slot 117 or, alternatively, from the second slot 117 to theretraction slot 129.

Another advantage of the curved end 157 of projection 122 is that itonly has point contact on ramp 150 as it moves across the ramp. Clearly,it is necessary that any flexion of the projection will be retained inthe slot in which it is located as any protrusion beyond that slot wouldfoul movement of the plunger relative to the wall of a surroundingbarrel.

Another embodiment of the present invention is shown in FIGS. 11-15.

In FIGS. 11A-11D and 12, it can be seen that plunger 415 has first slot416 interconnected to second slot 417 via first deviation 423, secondslot 417 interconnected to retraction slot 429 via second deviation 428,retraction slot 429 interconnected to fourth slot 470 via thirddeviation 472 and fourth slot 470 interconnected to first slot 416 viafourth deviation 471. First slot 416 and retraction slot 429 arelongitudinally offset with respect to each other; second slot 417 andfourth slot 470 are longitudinally offset with respect to each other;first deviation 423 and third deviation 471 are longitudinally offsetwith respect to each other; and second deviation 428 and fourthdeviation 472 are longitudinally offset with respect to each other; asindicated by arrows in FIGS. 11A-11B.

Referring to FIG. 12 and FIG. 13 in particular, collar 418 has body 462,barrel-engaging arms 464A and 464B, first projection 422A and secondprojection 422B which are longitudinally offset with respect to eachother. Furthermore, first projection 422A projects in a directionopposite to that of second projection 422B when assembled into syringe410, that is toward needle end 414.

Referring now to FIG. 14A, initially in use, first projection 422A islocated in first slot 416 and second projection 422B is located inretraction slot 429, maintained in this position by spring 480 whichbears against cap 481 (in use mounted to plunger 415) and collar 418.First slot 416 includes an abutment in the form of ramp 474. This ramp474 does not restrict slidable movement of projection 422A in first slot416. An abutment 475 is also located in retraction slot 429. Abutment475 in retraction slot 429 is block-shaped, although abutment 475 may bein the form of a ramp. Limited slidable movement of second projection422B (relative to plunger 415) is allowed in the direction of the arrowin FIG. 14A, such as when initially depressing plunger 415 to expel airfrom barrel 412.

Referring now to FIG. 14B, withdrawal of plunger 415 occurs to a pointwhere projections 422A and 422B move over and beyond abutment 474 andabutment 475 respectively. As previously described, projections 422A and422B are preferably resiliently flexible and are therefore tensioned asthey pass over ramp 474 and abutment 475 respectively. Projections 422Aand 422B then snap back into engagement with slots 416 and 429respectively. Because projection 422B faces guiding end 419 of barrel412, plunger 415 is prevented from slidable movement back in thedirection from which it came by second projection 422B bearing againstabutment 475. This restricts depression of plunger 415 so that anymaterial in the barrel cannot be expelled. Thus, completion of plunger415 withdrawal in the direction of the arrow in FIG. 14B must beperformed or else material in the syringe barrel cannot be injected.

It should be noted that because projections 422A and 422B arelongitudinally offset, as are fourth deviation 472 and second deviation428, in use projections 422A and 422B are guided along first slot 417and retraction slot 429 respectively, unable to be rotated back intofourth slot 470 and second slot 417 respectively. It is also noted thatabutments in the form of ledges 476A, 476B, 476C and 476D are providedthat assist in guiding the projections 422A and/or 422B into appropriateslots. These prevent undesirable movement of projection 422A or 422Bback into the deviation from whence they exited by virtue of projection422A and/or 422B bearing against the ledge located at the junction ofeach respective deviation and slot.

Completion of plunger withdrawal is followed by first projection 422Aslidably moving into second slot 417 via first deviation 423 and secondprojection 422B slidably moving from retraction slot 429 into fourthslot 470 via deviation 471. This causes a 90° C. rotation of plunger 415with respect to collar 418 and barrel 412.

Depression of plunger 415 to inject material in barrel 415 occurs whenfirst projection 422A is slidably located in second slot 417 and secondprojection 422B is slidably located in fourth slot 470.

As best seen in FIG. 15, second slot 417 has a plurality of abutments,in this case in the form of ramps 450A, 450B, 450C and 450D. As plunger415 is depressed to inject, first projection 422A bears against anyrespective one of ramps 450A, 450B, 450C and 450D to restrict retractionof plunger 415, in a similar fashion to that described in previousembodiments. Second projection 422B, however, is freely slidable withinfourth slot 470.

At the end or depression of plunger 415, needle end 414 of plunger 415is aligned with and engages needle 413 as hereinbefore described.

During retraction of needle 413, first projection 422A is moved intoretraction slot 429 via second deviation 428, while second projection422B moves from fourth slot 470 into first slot 416 via fourth deviation472. This results in a further 90° rotation of plunger 415 with respectto collar 418 and barrel 412. At the completion of retraction of needle413 into the position shown in FIG. 14C, plunger 415 has rotated a totalof 180°.

As shown in FIG. 14C, following retraction of plunger 415 and needle413, second projection 422B comes to bear against abutment 474 in firstslot 416 thereby preventing depression of plunger 415; first projection422A comes to bear against abutment 475 in retraction slot 429 therebypreventing withdrawal or retraction of plunger 415, thus rendering thesyringe 410 inoperable beyond first use.

Throughout the specification, the aim has been to describe the preferredembodiments of the invention without limiting the invention to any oneembodiment or specific collection of features. Various changes andmodifications may be made to the embodiments described and illustratedwithout departing from the present invention. In particular, it iscontemplated that gates, abutments, ledges and other means disclosedherein for restricting plunger movement may be readily interchanged asdesired by the skilled person.

1. A plunger for a single use syringe having a co-operating barrel and aretractable needle engaged therewith, said plunger engageable with saidretractable needle to facilitate retraction of said needle into saidbarrel, wherein said barrel has at least first and second projectionsand said plunger has a plurality of interconnected slots comprising afirst slot, a second slot, a retraction slot and a fourth slot, saidfirst slot connected to said second slot by a first deviation, saidsecond slot connected to said retraction slot by a second deviation,said retraction slot connected to said fourth slot by a third deviationand said fourth slot connected to said first slot by a fourth deviation,which slots are slidably engageable by the first and second projections,whereby initially said first projection is locatable in said first slotand is capable of slidably moving from said first slot through saidfirst deviation into said second slot and subsequently from said secondslot through said second deviation into said retraction slot; andinitially said second protection is locatable in said retraction slotand is capable of slidably moving from said retraction slot through saidthird deviation into said fourth slot and subsequently from said fourthslot through said fourth deviation into said first slot; wherein saidslots are arranged so that slidable movement of said respectiveprojections within said slots is restricted to thereby prevent re-use ofthe syringe.
 2. The plunger of claim 1, wherein the second slot includesa plurality of abutments engageable by said first projection to restrictwithdrawal of said plunger.
 3. The plunger of claim 1, wherein the firstslot includes an abutment engageable by said second projection torestrict depression of said plunger.
 4. The plunger of claim 1, whereinthe retraction slot includes an abutment engageable by said firstprojection to restrict withdrawal of said plunger after retraction iscomplete.
 5. The plunger of claim 1, wherein said retraction slotincludes an abutment engageable by said second projection to restrictdepression of said plunger.
 6. A single use retractable syringecomprising: a barrel; a retractable needle; and a plunger engageablewith said retractable needle to facilitate retraction of the needle intothe barrel, wherein the barrel has at least first and second projectionsand the plunger has a plurality of interconnected slots comprising afirst slot, a second slot, a retraction slot and a fourth slot, saidfirst slot connected to said second slot by a first deviation, saidsecond slot connected to said retraction slot by a second deviation,said retraction slot connected to said fourth slot by a third deviationand said fourth slot connected to said first slot by a fourth deviation,which slots are slidably engageable by the first and second projections,whereby initially said first projection is locatable in said first slotand is capable of slidably moving from said first slot through saidfirst deviation into said second slot and subsequently from said secondslot through said second deviation into said retraction slot; andinitially said second projection is locatable in said retraction slotand is capable of slidably moving from said retraction slot through saidthird deviation into said fourth slot and subsequently from said fourthslot through said fourth deviation into said first slot; wherein saidslots are arranged so that slidable movement of said respectiveprojections within said slots is restricted to thereby prevent re-use ofthe syringe.
 7. The syringe of claim 6, wherein the second slot includesa plurality of abutments engageable by the first projection to restrictwithdrawal of the plunger.
 8. The syringe of claim 6, wherein the firstslot includes an abutment engageable by the second projection torestrict depression of the plunger.
 9. The syringe of claim 6, whereinthe retraction slot includes an abutment engageable by the firstprojection to restrict withdrawal of the plunger after retraction iscomplete.
 10. The syringe of claim 6, wherein the retraction slotincludes an abutment engageable by the second projection to restrictdepression of the plunger.
 11. A method for making a single useretractable syringe, the method comprising: providing a barrel with aretractable needle adjacent one end of the barrel; and slidablydisposing at least a portion of a plunger in another end of the barrel,the plunger engageable with the retractable needle to facilitateretraction of the needle into the barrel, wherein the barrel has atleast first and second projections and the plunger has a plurality ofinterconnected slots comprising a first slot, a second slot, aretraction slot and a fourth slot, said first slot connected to saidsecond slot by a first deviation, said second slot connected to saidretraction slot by a second deviation, said retraction slot connected tosaid fourth slot by a third deviation and said fourth slot connected tosaid first slot by a fourth deviation, which slots are slidablyengageable by the first and second projections, whereby initially saidfirst projection is locatable in said first slot and is capable ofslidably moving from said first slot through said first deviation intosaid second slot and subsequently from said second slot through saidsecond deviation into said retraction slot; and initially said secondprojection is locatable in said retraction slot and is capable ofslidably moving from said retraction slot through said third deviationinto said fourth slot and subsequently from said fourth slot throughsaid fourth deviation into said first slot; wherein said slots have amovement restriction system so that slidable movement of the projectionswithin the slots is restricted to a first path to prevent re-use of thesyringe.
 12. The method of claim 11, wherein the second slot includes aplurality of abutments engageable by the first projection to restrictwithdrawal of the plunger.
 13. The method of claim 11, wherein the firstslot includes an abutment engageable by the second projection torestrict depression of the plunger.
 14. The method of claim 11, whereinthe retraction slot includes an abutment engageable by the firstprojection to restrict withdrawal of the plunger after retraction iscomplete.
 15. The method of claim 11, wherein the retraction slotincludes an abutment engageable by the second projection to restrictdepression of the plunger.
 16. The plunger of claim 2 further comprisingat least one recess adjacent at least one of the abutments, the at leastone recess is sized to provide a nesting position for at least one ofthe first and second projections.
 17. The plunger of claim 2 furthercomprising at least one undercut region in at least one of theabutments.
 18. The plunger as set forth in claim 2 wherein an outer edgeon at least one of the abutments is substantially parallel to anopposing surface on the one of the barrel and plunger with the pluralityof interconnected slots.
 19. The plunger as set forth in claim 2 whereina rear face on at least one of the abutments has an arc shape.
 20. Theplunger as set forth in claim 1 wherein the first and second projectionsextend in at least partially opposing directions.
 21. The syringe ofclaim 7 further comprising at least one recess adjacent at least one ofthe abutments, the at least one recess is sized to provide a nestingposition for at least one of the first and second projections.
 22. Thesyringe of claim 7 further comprising at least one undercut region in atleast one of the abutments.
 23. The syringe as set forth in claim 7wherein an outer edge on at least one of the abutments is substantiallyparallel to an opposing surface on the one of the barrel and plungerwith the plurality of interconnected slots.
 24. The syringe as set forthin claim 7 wherein a rear face on at least one of the abutments has anarc shape.
 25. The syringe as set forth in claim 6 wherein the first andsecond projections extend in at least partially opposing directions. 26.The method of claim 12 further comprising forming at least one recessadjacent at least one of the abutments, the at least one recess is sizedto provide a nesting position for at least one of the first and secondprojections.
 27. The method of claim 12 further comprising forming atleast one undercut region in at least one of the abutments.
 28. Themethod as set forth in claim 12 further comprising forming an outer edgeon at least one of the abutments which is substantially parallel to anopposing surface on the one of the barrel and plunger with the pluralityof interconnected slots.
 29. The method as set forth in claim 12 furthercomprising forming a rear face on at least one of the abutments whichhas an arc shape.
 30. The method as set forth in claim 11 furthercomprising forming the first and second projections to extend in atleast partially opposing directions.
 31. The plunger of claim 1, whereinthe plunger rotates into a position engageable with said needle at theend of depression of the plunger to facilitate retraction of saidneedle.
 32. The plunger of claim 31, wherein the plunger followingengagement of said retractable needle by said plunger, said plunger andneedle engaged therewith rotate into an inoperable position to preventre-use of the syringe.
 33. The plunger of claim 32, wherein said firstprojection and said second projection bear against respective abutmentsin respective slots of said plunger.
 34. The syringe of claim 6 whereinthe plunger rotates into a position engageable with said needle at theend of depression of the plunger to facilitate retraction of saidneedle.
 35. The syringe of claim 34 wherein the plunger followingengagement of said retractable needle by said plunger, said plunger andneedle engaged therewith rotate into an inoperable position to preventre-use of the syringe.
 36. The syringe of claim 35, wherein said firstprojection and said second projection bear against respective abutmentsin respective slots of said plunger.
 37. The method of claim 11 whereinthe plunger rotates into a position engageable with said needle at theend of depression of the plunger to facilitate retraction of saidneedle.
 38. The method of claim 37, wherein the plunger followingengagement of said retractable needle by said plunger, said plunger andneedle engaged therewith rotates into an inoperable position to preventre-use of the syringe.
 39. The method of claim 38, wherein said firstprojection and said second projection bear against respective abutmentsin respective slots of said plunger.
 40. The plunger of claim 1, whichis capable of rotating 180 degrees from when said first projection isinitially located in said first slot and said second projection isinitially located in said retraction slot to when said first projectionis located within said retraction slot; and initially said secondprojection is located in said first slot.
 41. The syringe of claim 6,which is capable of rotating 180 degrees from when said first projectionis initially located in said first slot and said second projection isinitially located in said retraction slot to when said first projectionis located within said retraction slot; and initially said secondprojection is located in, said first slot.